The invention relates to a method for operating, especially for starting, a fuel cell like especially a solid oxide fuel cell (SOFC). The invention further relates to a fuel cell arrangement comprising such a fuel cell, especially a SOFC hybrid system, for conducting this method.
Solid oxide fuel cells are used to convert fuel, such as hydrogen or a hydrogen rich compound, and oxygen to electric power, heat and hot output gases. The fuel is fed to an anode compartment of the fuel cell and oxygen is supplied by ambient or compressed air to a cathode compartment of the fuel cell.
Such a fuel cell is very vulnerable to internal temperature gradients which espedally occur during the start up procedure due to different thermal expansion properties of the different materials within the fuel cell.
JP 2001351665 discloses a composite electric generator and a method for starting such a generator, wherein the composite electric generator is composed of a gas turbine and a solid electrode fuel cell. An exhaust line of the gas turbine is fed through a combustion support burner; a pre-heater and a vapour generator in order to preheat the fuel and air which is supplied to the fuel cell. By this, a large temperature gradient at the fuel reformer at the start of the composite electric generator shall be prevented.
It is desirable to provide an improved method for operating a fuel cell as mentioned in the introductory part above especially during the start phase such that the temperature gradients which occur during the start phase are minimized, the risk of a premature damage of the fuel cell is decreased and the lifetime of the fuel cell is increased.
Another object underlying the invention is to provide a fuel cell arrangement comprising such a fuel cell which fuel cell arrangement is adapted for conducting the above method in an efficient manner.
By a method and arrangement according to aspects of the present invention, the problem of starting up a fuel cell (especially a SOFC) can be solved in a way which will not be destructive for the components of the fuel cell. The lifetime and the performance of the whole fuel cell hybrid arrangement can be prolonged. Furthermore, the lifetime of the catalyst of the fuel cell can also be prolonged due to the fact that less exothermic conditions occur at the start up procedure in comparison to known solutions. Finally, according to an aspect of the invention the option can be provided that the fuel cell hybrid arrangement can supply power by means of the turbine unit during the start up procedure.
It will be appreciated that features of the invention are susceptible to being combined in any combination without departing from the scope of the invention as defined by the accompanying claims.